Project Summary/Abstract In 2012, the Centers for Medicare and Medicaid Services implemented the Hospital Readmissions Reduction Program (HRRP), which penalizes hospitals with more 30-day readmissions than expected for myocardial infarction (MI), heart failure (HF), pneumonia (PNA), and, as of 2015, chronic obstructive pulmonary disease and arthroplasty of the hip and knee. Policymakers hope that the HRRP will improve clinical outcomes and reduce healthcare costs because readmissions are common among older adults, costly, and associated with mortality and functional decline. Yet black and low-income seniors are more likely to be readmitted, experience adverse outcomes of hospitalization, be treated at hospitals with limited resources, receive lower quality care, have limited access to primary care physicians and specialists, and have adverse social circumstances that make transitioning from the hospital to home more difficult. In addition, hospitals may respond to the HRRP in favorable ways, such as by improving inpatient and transition-related care, or in less favorable ones, such as by increasing barriers to readmission. Consequently, the HRRP could inadvertently exacerbate disparities between black and low-income seniors and their white and higher-income peers. This project will compare the effects of the HRRP on health outcomes (Aim One: mortality at 30, 60, and 180 days; and institutionalization at 180 days) and clinically important healthcare utilization (Aim Two: readmission, length of stay, emergency visits, observation stays, and use of formal post-acute care) between black vs. white, and Medicaid-dually-eligible vs. non-dually-eligible seniors. In addition, it will assess spillover effects on hospital-wide all-cause unplanned readmissions for black and dually-eligible seniors vs. their white and non-dually-eligible peers. Finally, the study will examine the extent to which the characteristics of the hospitals that seniors use and the neighborhoods where they reside explain disparities in the effects of the HRRP (Aim Three). The investigators will study episodes of care associated with hospitalizations for the conditions targeted by the policy that occur during baseline, and anticipation, and implementation periods, using an interrupted time- series analysis based on patient- and provider-level Medicare administrative data and other data sources. Econometric models will test for deviations in time trends for health and utilization outcome measures between the baseline vs. anticipation and implementation periods, adjust for patient-level control variables, and absorb hospital-level fixed effects. In addition to assessing the HRRP's effects on disparities in health outcomes that are important to older adults, the study will use simulation models enabling results to be reported in a format that is easy for policymakers and stakeholders to understand.